Proceedings of the Third All-Union Mathematical Congress , the editor of which was the famous mathematician Sergei Mikhailovich Nikolsky , is a unique collection of scientific papers, collected during one of the most important events in the world of mathematics - the Third All-Union Mathematical Congress . This publication not only reflects the achievements and trends of mathematical science in the Soviet Union, but also serves as a valuable source for researchers, students and anyone interested in the development of mathematics in the 20th century. The Congress, held in 1969, brought together under one roof the leading mathematicians of the country, who discussed current problems and the latest achievements in various fields of mathematics. The book presents works covering a wide range of topics from number theory and algebra to functional analysis and mathematical logic. Each article is not just a scientific work, but the result of deep reflection and research that can be of interest to both professional mathematicians and students seeking to expand their knowledge. This book will be especially useful for those who are fond of mathematics and want to immerse themselves in the atmosphere of scientific discussion and exchange of ideas. Students and graduate students studying mathematics will find in it a lot of useful materials that will help them in their studies and scientific activities. It can also attract the attention of teachers who want to enrich their lectures with examples from real scientific practice. The topics raised in the Proceedings of the Third All-Union Mathematical Congress cover not only highly specialized issues, but also broader philosophical and methodological aspects of mathematics. For example, issues related to the relationship of mathematics with other sciences are discussed, as well as the role of mathematics in solving practical problems, which makes the book relevant for representatives of related disciplines. Sergey Mikhailovich Nikolsky, as an editor, brought to the collection his unique style and deep understanding of the subject. He is known for his work in the field of functional analysis and operator theory, which, of course, affected the quality and content of the materials presented. Nikolsky is also the author of other significant works, such as Functional Analysis and Operator Theory, which have become classics in their field. Reading the Proceedings of the Third All-Union Mathematical Congress, you will not only enrich your knowledge in the field of mathematics, but also be able to appreciate how science developed in the conditions of the Soviet era. This edition is not just a collection of articles, but a whole era imprinted on the pages, which continues to inspire new researchers and students. If you are interested in topics such as the history of mathematics, scientific conferences, achievements in the field of number theory or functional analysis, then this book will be a real find for you. It will not only expand your horizons, but also help you understand how mathematics was formed and developed in different historical periods. The Proceedings of the Third All-Union Mathematical Congress is not just a scientific publication, but an important contribution to the treasury of knowledge that will be useful to many generations of readers.